My new "hide" seems to be working quite well. I've hung a sheet up over the back door, and cut a hole in it for the camera lens. Another smaller hole allows me to peek through. I can sit indoors with an eye on the garden. When I see some action I just move to the back door and hope that I don't spook them.
The TV can be heard in the garden, but this doesn't seem to bother the foxes too much. The clicking of the camera is quite loud, but I think that they might have got used to that. On the other hand, the slightest creak of a floorboard, or the sound of the camera's autofocus, or any "tapping" sound all seem to spook them. Their hearing is absolutely astonishing.